1. Field of the Invention
This invention relates to improvements in color monitors, and more particularly to improvements in methods and apparatus for controlling the color saturation of a color monitor.
2. Relevant Background
In the past, personal computer users have experienced frustration with color displays or monitors that have provided only image brightness and contrast controls, but provided no control to change or adjust the color saturation of the image. The brightness of an image refers to the luminance of the image apart from its hue or saturation, whereas contrast refers to the brightness ratio of the lightest to the darkest part of the image. The saturation of a color of an image refers to the degree of chroma or purity of the color, or the degree of freedom from admixture with white.
Often with many modern software programs, the saturation of the color may need to be modified, but no control is provided to accomplish such change or adjustment. Although the television display art may appear relevant, since television monitors often include a color saturation control, major differences exist. This may be due in part to the differences in the ways that video signals are processed by television monitors and color monitors used with personal computers or the like. For ease of description, standard color television monitors and receivers of the type in which four video signals are supplied or derived, including a black and white luminance signal, and at least two color difference signals that are processed with the luminance signal to produce a composite video signal, are referred to herein as "television monitors". Color monitors used in applications such as personal computer displays, or the like, of the type in which three color video signals are supplied and individually displayed on a screen or other display device without the presence of a separate black and white luminance signal, are referred to as "color monitors".
In contrast to color monitors widely known in the computer industry, television monitors typically process video signals that are transmitted as a composite video signal that has a luminance, or black and white, signal that is combined with a chromanance signal. The separate luminance signal is required to enable the signal to be viewable on black and white television receivers. The presence of both luminance and chromanance signals makes the provision of a color saturation control desirable, and easily providable.
However, color monitors do not require the separate luminance signal, and, as mentioned, typically do not have a separate color saturation control. This often results in colors being distorted, being displayed as the wrong color, or masking information to be displayed, especially if the hues of adjacent colors are close. As an example, if a red background had maroon letter displayed on it, and the saturation of the colors were too high, conceivably, the colors would all display the same, and the letters could not be discerned from the background.
In accomplishing such color saturation control in television monitors, generally two signals, a video signal and a chroma signal, are provided. The video signal represents essentially a black and white picture. The chroma signal provides color to the video signals generally and is typically made up of three color signals, red (R), blue (B) and green (G). The color signals are usually repressed as a color difference between a color component signal and the video signal. Thus, one or more of the color difference signals may be derived at the receiver if a sufficient number of the other color signals are known.
On the other hand, in typical color monitors used in personal computers, or similar applications, the signals needed to drive the monitor are merely the three color signals unaccompanied by a separate black and white video signal. Thus, the standard video solution is inapposite to providing color saturation control in color monitors, or the like.